<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    
    <title>29.2. codeop — Compile Python code &mdash; Python v2.6.2 documentation</title>
    <link rel="stylesheet" href="../_static/default.css" type="text/css" />
    <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
    <script type="text/javascript">
      var DOCUMENTATION_OPTIONS = {
        URL_ROOT:    '../',
        VERSION:     '2.6.2',
        COLLAPSE_MODINDEX: false,
        FILE_SUFFIX: '.html',
        HAS_SOURCE:  true
      };
    </script>
    <script type="text/javascript" src="../_static/jquery.js"></script>
    <script type="text/javascript" src="../_static/doctools.js"></script>
    <link rel="search" type="application/opensearchdescription+xml"
          title="Search within Python v2.6.2 documentation"
          href="../_static/opensearch.xml"/>
    <link rel="author" title="About these documents" href="../about.html" />
    <link rel="copyright" title="Copyright" href="../copyright.html" />
    <link rel="top" title="Python v2.6.2 documentation" href="../index.html" />
    <link rel="up" title="29. Custom Python Interpreters" href="custominterp.html" />
    <link rel="next" title="30. Restricted Execution" href="restricted.html" />
    <link rel="prev" title="29.1. code — Interpreter base classes" href="code.html" />
    <link rel="shortcut icon" type="image/png" href="../_static/py.png" />
 

  </head>
  <body>
    <div class="related">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="../genindex.html" title="General Index"
             accesskey="I">index</a></li>
        <li class="right" >
          <a href="../modindex.html" title="Global Module Index"
             accesskey="M">modules</a> |</li>
        <li class="right" >
          <a href="restricted.html" title="30. Restricted Execution"
             accesskey="N">next</a> |</li>
        <li class="right" >
          <a href="code.html" title="29.1. code — Interpreter base classes"
             accesskey="P">previous</a> |</li>
        <li><img src="../_static/py.png" alt=""
                 style="vertical-align: middle; margin-top: -1px"/></li>
        <li><a href="../index.html">Python v2.6.2 documentation</a> &raquo;</li>

          <li><a href="index.html" >The Python Standard Library</a> &raquo;</li>
          <li><a href="custominterp.html" accesskey="U">29. Custom Python Interpreters</a> &raquo;</li> 
      </ul>
    </div>  

    <div class="document">
      <div class="documentwrapper">
        <div class="bodywrapper">
          <div class="body">
            
  <div class="section" id="module-codeop">
<h1>29.2. <tt class="xref docutils literal"><span class="pre">codeop</span></tt> &#8212; Compile Python code<a class="headerlink" href="#module-codeop" title="Permalink to this headline">¶</a></h1>
<p>The <tt class="xref docutils literal"><span class="pre">codeop</span></tt> module provides utilities upon which the Python
read-eval-print loop can be emulated, as is done in the <a title="Facilities to implement read-eval-print loops." class="reference external" href="code.html#module-code"><tt class="xref docutils literal"><span class="pre">code</span></tt></a> module.  As
a result, you probably don&#8217;t want to use the module directly; if you want to
include such a loop in your program you probably want to use the <a title="Facilities to implement read-eval-print loops." class="reference external" href="code.html#module-code"><tt class="xref docutils literal"><span class="pre">code</span></tt></a>
module instead.</p>
<p>There are two parts to this job:</p>
<ol class="arabic simple">
<li>Being able to tell if a line of input completes a Python  statement: in
short, telling whether to print &#8216;<tt class="docutils literal"><span class="pre">&gt;&gt;&gt;</span></tt>&#8216; or &#8216;<tt class="docutils literal"><span class="pre">...</span></tt>&#8216; next.</li>
<li>Remembering which future statements the user has entered, so  subsequent
input can be compiled with these in effect.</li>
</ol>
<p>The <tt class="xref docutils literal"><span class="pre">codeop</span></tt> module provides a way of doing each of these things, and a way
of doing them both.</p>
<p>To do just the former:</p>
<dl class="function">
<dt id="codeop.compile_command">
<tt class="descclassname">codeop.</tt><tt class="descname">compile_command</tt><big>(</big><em>source</em><span class="optional">[</span>, <em>filename</em><span class="optional">[</span>, <em>symbol</em><span class="optional">]</span><span class="optional">]</span><big>)</big><a class="headerlink" href="#codeop.compile_command" title="Permalink to this definition">¶</a></dt>
<dd><p>Tries to compile <em>source</em>, which should be a string of Python code and return a
code object if <em>source</em> is valid Python code. In that case, the filename
attribute of the code object will be <em>filename</em>, which defaults to
<tt class="docutils literal"><span class="pre">'&lt;input&gt;'</span></tt>. Returns <tt class="xref docutils literal"><span class="pre">None</span></tt> if <em>source</em> is <em>not</em> valid Python code, but is a
prefix of valid Python code.</p>
<p>If there is a problem with <em>source</em>, an exception will be raised.
<a title="exceptions.SyntaxError" class="reference external" href="exceptions.html#exceptions.SyntaxError"><tt class="xref docutils literal"><span class="pre">SyntaxError</span></tt></a> is raised if there is invalid Python syntax, and
<a title="exceptions.OverflowError" class="reference external" href="exceptions.html#exceptions.OverflowError"><tt class="xref docutils literal"><span class="pre">OverflowError</span></tt></a> or <a title="exceptions.ValueError" class="reference external" href="exceptions.html#exceptions.ValueError"><tt class="xref docutils literal"><span class="pre">ValueError</span></tt></a> if there is an invalid literal.</p>
<p>The <em>symbol</em> argument determines whether <em>source</em> is compiled as a statement
(<tt class="docutils literal"><span class="pre">'single'</span></tt>, the default) or as an <a class="reference external" href="../glossary.html#term-expression"><em class="xref">expression</em></a> (<tt class="docutils literal"><span class="pre">'eval'</span></tt>).  Any
other value will cause <a title="exceptions.ValueError" class="reference external" href="exceptions.html#exceptions.ValueError"><tt class="xref docutils literal"><span class="pre">ValueError</span></tt></a> to  be raised.</p>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">It is possible (but not likely) that the parser stops parsing with a
successful outcome before reaching the end of the source; in this case,
trailing symbols may be ignored instead of causing an error.  For example,
a backslash followed by two newlines may be followed by arbitrary garbage.
This will be fixed once the API for the parser is better.</p>
</div>
</dd></dl>

<dl class="class">
<dt id="codeop.Compile">
<em class="property">
class </em><tt class="descclassname">codeop.</tt><tt class="descname">Compile</tt><a class="headerlink" href="#codeop.Compile" title="Permalink to this definition">¶</a></dt>
<dd>Instances of this class have <a title="object.__call__" class="reference external" href="../reference/datamodel.html#object.__call__"><tt class="xref docutils literal"><span class="pre">__call__()</span></tt></a> methods identical in signature to
the built-in function <a title="compile" class="reference external" href="functions.html#compile"><tt class="xref docutils literal"><span class="pre">compile()</span></tt></a>, but with the difference that if the
instance compiles program text containing a <a title="Future statement definitions" class="reference external" href="__future__.html#module-__future__"><tt class="xref docutils literal"><span class="pre">__future__</span></tt></a> statement, the
instance &#8216;remembers&#8217; and compiles all subsequent program texts with the
statement in force.</dd></dl>

<dl class="class">
<dt id="codeop.CommandCompiler">
<em class="property">
class </em><tt class="descclassname">codeop.</tt><tt class="descname">CommandCompiler</tt><a class="headerlink" href="#codeop.CommandCompiler" title="Permalink to this definition">¶</a></dt>
<dd>Instances of this class have <a title="object.__call__" class="reference external" href="../reference/datamodel.html#object.__call__"><tt class="xref docutils literal"><span class="pre">__call__()</span></tt></a> methods identical in signature to
<a title="codeop.compile_command" class="reference internal" href="#codeop.compile_command"><tt class="xref docutils literal"><span class="pre">compile_command()</span></tt></a>; the difference is that if the instance compiles program
text containing a <tt class="docutils literal"><span class="pre">__future__</span></tt> statement, the instance &#8216;remembers&#8217; and
compiles all subsequent program texts with the statement in force.</dd></dl>

<p>A note on version compatibility: the <a title="codeop.Compile" class="reference internal" href="#codeop.Compile"><tt class="xref docutils literal"><span class="pre">Compile</span></tt></a> and
<a title="codeop.CommandCompiler" class="reference internal" href="#codeop.CommandCompiler"><tt class="xref docutils literal"><span class="pre">CommandCompiler</span></tt></a> are new in Python 2.2.  If you want to enable the
future-tracking features of 2.2 but also retain compatibility with 2.1 and
earlier versions of Python you can either write</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">try</span><span class="p">:</span>
    <span class="kn">from</span> <span class="nn">codeop</span> <span class="kn">import</span> <span class="n">CommandCompiler</span>
    <span class="n">compile_command</span> <span class="o">=</span> <span class="n">CommandCompiler</span><span class="p">()</span>
    <span class="k">del</span> <span class="n">CommandCompiler</span>
<span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
    <span class="kn">from</span> <span class="nn">codeop</span> <span class="kn">import</span> <span class="n">compile_command</span>
</pre></div>
</div>
<p>which is a low-impact change, but introduces possibly unwanted global state into
your program, or you can write:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">try</span><span class="p">:</span>
    <span class="kn">from</span> <span class="nn">codeop</span> <span class="kn">import</span> <span class="n">CommandCompiler</span>
<span class="k">except</span> <span class="ne">ImportError</span><span class="p">:</span>
    <span class="k">def</span> <span class="nf">CommandCompiler</span><span class="p">():</span>
        <span class="kn">from</span> <span class="nn">codeop</span> <span class="kn">import</span> <span class="n">compile_command</span>
        <span class="k">return</span> <span class="n">compile_command</span>
</pre></div>
</div>
<p>and then call <tt class="docutils literal"><span class="pre">CommandCompiler</span></tt> every time you need a fresh compiler object.</p>
</div>


          </div>
        </div>
      </div>
      <div class="sphinxsidebar">
        <div class="sphinxsidebarwrapper">
            <h4>Previous topic</h4>
            <p class="topless"><a href="code.html"
                                  title="previous chapter">29.1. <tt class="docutils literal docutils literal"><span class="pre">code</span></tt> &#8212; Interpreter base classes</a></p>
            <h4>Next topic</h4>
            <p class="topless"><a href="restricted.html"
                                  title="next chapter">30. Restricted Execution</a></p>
            <h3>This Page</h3>
            <ul class="this-page-menu">
              <li><a href="../_sources/library/codeop.txt"
                     rel="nofollow">Show Source</a></li>
            </ul>
          <div id="searchbox" style="display: none">
            <h3>Quick search</h3>
              <form class="search" action="../search.html" method="get">
                <input type="text" name="q" size="18" />
                <input type="submit" value="Go" />
                <input type="hidden" name="check_keywords" value="yes" />
                <input type="hidden" name="area" value="default" />
              </form>
              <p class="searchtip" style="font-size: 90%">
              Enter search terms or a module, class or function name.
              </p>
          </div>
          <script type="text/javascript">$('#searchbox').show(0);</script>
        </div>
      </div>
      <div class="clearer"></div>
    </div>
    <div class="related">
      <h3>Navigation</h3>
      <ul>
        <li class="right" style="margin-right: 10px">
          <a href="../genindex.html" title="General Index"
             >index</a></li>
        <li class="right" >
          <a href="../modindex.html" title="Global Module Index"
             >modules</a> |</li>
        <li class="right" >
          <a href="restricted.html" title="30. Restricted Execution"
             >next</a> |</li>
        <li class="right" >
          <a href="code.html" title="29.1. code — Interpreter base classes"
             >previous</a> |</li>
        <li><img src="../_static/py.png" alt=""
                 style="vertical-align: middle; margin-top: -1px"/></li>
        <li><a href="../index.html">Python v2.6.2 documentation</a> &raquo;</li>

          <li><a href="index.html" >The Python Standard Library</a> &raquo;</li>
          <li><a href="custominterp.html" >29. Custom Python Interpreters</a> &raquo;</li> 
      </ul>
    </div>
    <div class="footer">
      &copy; <a href="../copyright.html">Copyright</a> 1990-2009, Python Software Foundation.
      Last updated on Apr 15, 2009.
      Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 0.6.1.
    </div>
  </body>
</html>